Sometimes sending emails can take longer than expected. This can cause a server timeout and wrong statistics in some cases. You’ll get a notification in this case:
Also if you’re on the cron.php page you get this
If this is a temporary problem and the notification box vanishes by itself you can ignore it but should consider following things if it happens regularly :
- Increase your server’s memory limit
- Decrease the mails sent at once at Settings => Newsletter => Delivery
You can also calculate your sending limits.